class Bit: def __init__(self, a): self.a = a self.n = len(a) self.bit = [0] * (self.n + 1) for i, x in enumerate(a): self.update(i+1, x) def update(self, x, val): while x <= self.n: self.bit[x] += val x += x & -x def query(self, x): sum = 0 while x > 0: sum += self.bit[x] x -= x & -x return sum
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